Shock-absorber.



W. T. CLARK.

SHOCK ABSORBER.

APPLICATION FILED NOV. 28. 1913.

LIQU 357D Patented May 25, 1915.

2 SHEETS-SHEET I.

V WITNESSES THE NORRIS PETERS 60., PHOTO-LITHQ. WASHINGTON, D4 C W. T. CLARK.

SHOCK ABSORBER.

APPLICATION FILED NOV 23, I913 1,14Q357D Patented May 25, 1915.

2 SHEETS-SHEET 2.

WITNESSES. m W

THE NORRIS PETERS co., PHOTO LITHO., WASHINGTON, D. C.

UNTTFED STATES PATENT @FFTQE.

WILLIAIVI T. CLARK, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

SHOCK-ABSORBER.

Application filed November 28, 1913.

To all whom it may concern Be it known that I, WVILLIAM T. CLARK; a citizen of the United States, residing in Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a new and useful Improvement in Shock- Absorbers, of which the following is a specification.

My invention relates to a shock absorber for gearing, and one of its objects is to provide a device especially applicable to that type of gears known as tandem gears in common use with electric elevators, which device is simple in construction and has the effect of taking up any jar or shock which may be present in such gears. This and other objects of the invention will appear in the following specification in which I will describe an embodiment and at the end of which I will set forth its novel features in claims.

Referring to the drawings; Figure 1 is a diagrammatic view of certain parts of a common form of elevator employing tandem gearing, and shows my invention applied thereto; Fig. 2 is a sectional side elevation of a device embodying my invention; Figs. 3, 1 and 5, are diagrammatic views of certain parts of the gearing to which my invention is applied, and these figures are shown for the purpose of illustrating the operation of the device; Fig. 6 is a wiring diagram of electrical circuits of a typical electric elevator containing an embodiment of my in vention.

Referring to Fig. 1, I show a reversible electric motor 10 which is connected to rotate a shaft 11 in both directions. Two oppositely pitched worms 12 and 13 are upon this shaft and these worms mesh respectively with worm gears 14 and 15 which are also in mesh with each other or are otherwise connected to run together. On the shaft of gear 15 is mounted a rope or cable drum 16. From one side of this drum a cable 17 runs up over a sheave 18 at the top of the elevator hatchway, and is fastened to the car 19. I

20 is a bacledrum counterweight, tliat is it is connected with the back of the hoisting drum 16 by a rope or cable 21 which runs over a supporting sheave 22 and a guiding sheave 23 to the drum. If, as is sometimes the case, the hoisting mechanism is located Specification of Letters Patent.

Patented May 25, 1915.

Serial No. 803,,385.

at the top of the shaft, the sheaves 18, 22, and 23 may be omitted.

The foregoing parts have been described but briefly for they do not of themselves form any part of the present invention.

As is well known, gearing of this and similar character requires no end thrust bearings for the intermeshing gears balance each other so far as end thrust is concerned. But it has been found that if there is any play or backlash between the teeth of the gears, and worms, there is not only a disagreeable jar felt in the car, especially upon reversing, but that the severe strains put upon the gears under present elevator practice due to sudden starting and stopping of the car increase this defect rapidly. I have found that the blow between the teeth may be cushioned and the resulting shock absorbed or eliminated by the use of some such simple device as that which I am about to describe herewith. As will appear more fully, an unusual smoothness of operation is attained, and the wear on the gearing itself is greatly reduced as well as cable strains in starting and stopping cushioned.

Briefly, my novel shock absorber comprises an electrically controlled pressure device with means for applying a resilient pressure or stress upon one end or the other of the worm shaft 11 tending to move it longitudinally, and is an improvement upon the spring actuated shock absorber disclosed in United States Patent, No. 1,087,205, issued to me on September 3, 1912, for shock absorber for gearings.

Referring to Fig. 2, I will describe the construction of a simple form of my device. The reference numeral 24 designates the gear casing of the hoisting mechanism at the end of the shaft 11 in which casing the shaft is supported. This device comprises a housing 30 of iron or other magnetic material which is adapted to be fastened by bolts 85, 85, onto the end of the casing 24 in place of the cap which is usually placed over the end of the shaft hole. This housing 30 contains a magnet winding 32 which is wound upon a spool 33 forming a solenoid within which lies the worm shaft 11 itself or a piece of soft iron 31 secured to the end of the worm shaft. A soft iron plug 86 is screwed into one end of the housing 30 and may be secured in adjusted position by means of to leave an air gap between the two even when the magnet is fully eigcited.

It may be seen that this simple device may readily be placed upon elevator mechanisms already installed and in daily operation, and it may be made to exert an end pressure upon the shaft 11 varying in amount in accordance with the strength of the magnet32 and the adjustment of the screw plug 36.

I will describe the operation of my invention by making reference to the diagrams, Figs. 3, i and 5. It will be understood that the counterweight 20' is heavier than the car19, so that when there is but a light load in-the car the pull on rope or cable 21 will be greater than the pull on the rope 17. When the car is fully loaded, this condition will be reversed. Let us assume first that the load on the car, together with the weight of the car itself just balances the counterweight 20. The weightsthen will have no tendency to'rotate the drum 16 and the gears Hand 15. Let us further assume that there is some play or back lash between the worms 12,13, and gears 14, 15, respectively. Without my device applied the shaft 11 is free to float, that is to move back and forth longitudinallyr With the conditions assumed and illus trated diagrammatically in Fig. 3, the shaft may assume a position with the teeth of the worms midway between the teeth of the gears. In starting to rotate the shaft'll in either direction there will be a jar or shock when the teeth-of the worms strike against the teeth of the gears; this difliculty will be greatly aggravated if the car and counterweight loads do not balance and theshaft 11 is rotated in a direction opposite to that of greatest pressure on the gearing.

Referring now to Fig. 4, it will beassumed for purposes of' illustration, that there is 6000 lbs; more strain putupon gears 14: and 15 by the counterweight than by the car." The condition then will be that this 6000 lbs; will be taken up equally at the revolved, the tendency is for the worm toothto advance and strike tooth E of gear 15. But with resilient pressure, applied at one end of shaft 11, the latter is caused to move longitudinally, maintaining the contact 'between the worm and gear vat'B. It is in this manner that the j ar of starting'the elevator with gears of this general type is cushioned and overcome.

Now considering Fig. 5 and assuming that the pull of the car on gear 15 is 6000 lbs, greater than that of the counterweight. This pull will be divided between the points F and G. But with'500 lbs., resilient longitudinal pressurein the'directionof the arrow 0, the pressure will be unequally divid'ed and there will be 3500 lbs. pressure at.

Fand- 2500- lbsrpressure at G. Running'the elevator under these conditions will make gear 14 do the greater part of When the driving'pressure is worm 12 and the work. reversed and-thework revolved, the resilient end pressure upon the shaft will shift the latter to preventthe backof the worm tooth of worm 12 striking against tooth H of gear 14. 1

In the usual constructions, the worms 12 and 13 are made of steel and the gears 14 and 15 of bronze. The latter are capable of long wear but are peculiarly susceptible rection,that is, the annular acceleration of' the worm timesthe-lead ofthe screw. The

figures used in explaining the foregoing op-,

erations are arbitrarily selected for'illustration only. I V

Not only does this invention decrease the wear of the gears, but it may nowbe 'seen that the operation on thecar will be sm'oother when starting and stopping due to the fact that the worms and gears are'held in contact, and that sudden strains throughout the ropes and other parts ofthehoisting apparatus will be greatly relieved.

lVhile it would be possible and practical to maintain the magnet'32 of the shock absorber energized atall times, there is no necess'ity of having it consume current'ex'cept during-the starting and stopping period. In order therefore, to save current an'd' to employ a magnetof moderate size without danger'of overheating, I have devised a system of electrical circuits shown in Fig. 6.

Referring to Fig.6, I show a car switch 37 adapted to close a circuit to either of the reversing switches '38 and 39 which in turn close a circuit to the motor 10 for either direction of rotation. An accelerating magnet 40 is connected by the reversing switches across the motor armature and operates automatically to short circuit the contacts 1, 2, 3, 4 and 5 in the order named, successively to cut out the starting resistance 44 in starting the motor. The contact 3 carries an insulated contact which is one of a pair of contacts 6, which are normally in closed position when the motor is slowing down or at rest. A resistance 43 is arranged to be thrown across the motor armature when the reversing switches 38 and 39 are in lowermost position and its function is to provide a dynamic brake action on the motor tending to stop it. The usual electric brake apparatus I have not shown but it is to be understood that I contemplate using such brake arranged and connected in the customary manner. A relay 44 controls a pair of contacts 45 and is connected across the motor armature. 46 designates a resistance which is normally in series with the magnet 32 and shunt field winding 42 of the motor.

The operation of the above described system of circuits is as follows: With the parts in the position shown and the motor at rest, a circuit is maintained from the main through the resistance 46 and through the magnet 32 and contacts 5 in series and also through the motor field 42. The ohmic resistance of the resistance 46 and the magnet 32 is of such value that but a very feeble current flows in the magnet 32 and its pull on the shaft 11 is practically negligible. As soon as either of the reversing switches 38, 39, is raised to start the motor, the resistance 46 is short circuited and the magnet 32 and motor field receive full current from the mains and the motor starts with the pull on the shaft 11 at a maximum. As soon as the motor has accelerated to substantially one half full speed the contacts 3 are automatically closed by the accelerating magnet 40 and the contacts 6 simultaneously opened, thereby interrupting the circuit to the magnet 32. In stopping the elevator, the reversing switch is dropped, thereby closing a short circuit around the motor armatur including the resistance 43, and at the same time interrupting the circuit to the accelerating magnet 40 at one of the contacts 47. The contact 6 immediately close, again establishing the circuit to the magnet 32 and also an additional circuit to this magnet from the main by way of the contacts 45 of the relay 44, which latter being connected across the motor armature is now in raised position. The resistance 46 is short circuited and the magnet 32 and motor field receive full line current, as long as the relay remains in raised position. The relay 44 is so connected and arranged that it will remain in raised position until the motor counter electro motive force practically disappears, or in other words until the motor substantially comes to rest, hence the dynamic brake action upon the motor takes place under maximum field strength and the pull exerted by the magnet 32 on the worm shaft is effective during the entire stopping period of the motor. Then the motor finally comes to rest the relay 44 becomes dead and the contacts 45 are opened and the resistance 46 is once more included in the circuit of the relay 32 and motor field.

In reviewing this operation it will be seen that the magnet 32 of the shock absorber is very slightly energized when the motor is at rest and is fully energized during the acceleration and deceleration of the motor. The slight energization of the magnet 32 insures that it will immediately come up to full strength upon closing the motor circuit so that the maximum pull of the shock absorber is available the instant the motor circuit is closed and the worm shaft 11 exerts a driving torque. Since the magnet 32 only takes an appreciable current during the starting and stopping period the current consumed by the shock absorber is reduced to a minimum and is only used when most needed. For this reason the magnet 32 may be very moderate in size and still be free from danger of overheating, whereas if the magnet took full current at all times it would have to be much larger and more expensive to construct.

While the system of electrical circuits shown in Fig. 6 will accomplish the de sired end, said system is only illustrative of one method of control, and it is observed that other arrangements of circuits could easily be devised so as to produce the proper action of the shock absorber. Moreover the arrangement and construction of the shock absorber itself is illustrated in its simplest form but I do not limit myself to this specific arrangement of parts or to the specific arrangement of electrical circuits.

If desired the magnet 32 could easily be arranged to exert a thrust or end pressure upon the shaft 11 in the opposite direction to that shown, or the magnet could be located at an intermediate position on the shaft or at the other end of the shaft if so desired, the ultimate result being the same in each case.

What I claim is 1. In an elevator, tandem gearing comprising a shaft having oppositely pitched worms thereon, and magnetic means for applying a longitudinal stress in said shaft.

2. In an elevator, a shaft having right and left hand worms, gears meshing with said worms and connected with each other, and electrical means for applying a longitudinal stress in said shaft.

3. In an elevator, a shaft having right and left hand worms, gears meshing with said Worms and connected with each other, and electrical means tending to effect a longitudinal movement of said shaft.

a. In an elevator, a shaft having right and left hand Worms, gears meshing with said Worms and with eachother, and mag- 7 netic means for exerting a longitudinal pull on said shaft.

5. In an elevator, a shaft having right and left hand worms,'gears meshing with said worms and with each other, and magnetic means for exerting a longitudinal pull on one end of said shaft.

6. In an elevator, a shaft having right and left hand worms, gears meshing with said Worms, and connected with eachother, and an electromagnetic shock absorber arranged to effect a longitudinal movement of the said shaft.

7. In an elevator, a shaft having right and left hand Worms, gears meshing with said Worms and connected with each other, an electromagnetic shock absorber adapted to efiect a longitudinal stress in said shaft, and means for adjusting the amount of said stress.-

8. In an elevator, tandem gearing comprising a shaft having oppositely pitched prising a shaft having oppositely pitched" worms thereon, gears meshing With said Worms and arranged to drive eachj other, an

electromagnetic device for moving said shaft longitudinally, means for rotating said shaft, and means controlled by said shaft r0- tating'meansfor effecting the operation of said devic'efi 11. In anelevator, tandemgearing comprising a shaft having oppositely pitched worms thereon, gears meshing with said Worms and arranged to drive each other, a

motor arranged to rotate said shaft, and, means controlled by said motor for effecting a longitudinal stress in said shaft. I

l2.--In an-elevator, tandem-gearing com-' prising a shaft having oppositely pitched worms thereon, gears meshing with said.

Worms andarranged to drive each other, a motor arrangedto rotate said shaft, an electromagnetic device arranged to effect a longitudinal pull upon said shaft, and a circuit for said device controlled by the motor in starting and stopping;

13. In an elevator,1tandem gearing comprising a shaft having oppositely pitched worms thereon, gears meshing with said Worms and arranged to drive each other, a motor arranged to rotate said shaft, an electromagnetic device arranged to effect a longitudinal pull up'onsaid shaft, and means for fully energizing said electromagnetic device When the motor is accelerating and decelerating and for partially energizing the said device while the motor is atrest.

In testimony whereof, I. have signed my name to this specification in the presence of two subscribing witnesses. V

WILLIAM T. CLARK.

Witnesses: 1

WALTER C. STRANG, JAMES Gr. BETHELL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D43. 

